It is not surprising that blue topaz has become one of the top selling gems in the jewellery business. Blue topaz is unusual in offering excellent hardness (8 on the Mohs scale) and brilliance at a very reasonable cost.
Blue topaz can be found in both lighter and darker tones, usually known in the trade as sky blue topaz, Swiss blue topaz and London blue topaz. As in the case of other blue gems, the more saturated blues tend to have a higher value. So in topaz it is the London blue that usually regarded as the most valuable.
London blue topaz is a medium to dark greyish blue, sometimes described as “steely” or “inky”. Many London blue gems have a slightly greenish tone when viewed from certain angles.
The Greeks believed that this gemstone had the power to enhance the strength of the wearer and Egyptians wore it to protect themselves from injuries. Romans believed that it had the power to improve weak eye sight.